I just got replacements for the suspected bad DS8880 display driver IC in the HP 432C RF Power Meter I was looking at a few months ago and got ambitious and finished troubleshooting it.
Used Photoshop to convert to B&W and mark up a pic of the driver board underside to document the connections:
![](https://photos.smugmug.com/Electronics/HP-432C-Power-Meter/i-8G5fmSh/0/4d7cdd36/XL/HP%20432C%20Panaplex%20Display%20Module%20bottom%20view%20BW%20crop-XL.jpg)
(the problem child is the 'a' segment of the most significant digit on the left)
Soldered cut off leads to the 'a' segment connection on the IC and the ground pin, then turned things on to confirm that the display was still bad (didn't think it was a cold solder joint, but hope springs eternal...) - as expected, the problem was still there:
![](https://photos.smugmug.com/Electronics/HP-432C-Power-Meter/i-CZm8BPk/0/c4a3f463/XL/HP%20432C%20display%20pwrd%20w%20test%20point%20taps-XL.jpg)
Grounding the missing segment through a 330Ω resistor (straight to ground caused the missing segment to be at a lower potential than the others being switched by the chip, extinguishing them) got it to light, giving the display end inter-board connections a clean bill of health and confirming the IC has failed:
![](https://photos.smugmug.com/Electronics/HP-432C-Power-Meter/i-C383k5J/0/4051165a/XL/HP%20432C%20display%20a%20segment%20gndd-XL.jpg)
Now I need to dismantle the display and replace the faulty IC - hope to find time later today to do so, but must hit the sack now as it's almost six AM in these parts.
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
-Pat